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amfast - EncodeAndDecode.wiki

Encoder and Decoder

Type Map

  • How types are mapped between Python and AMF

Python -> AS3

| Python | AS3 | |:-------|:----| | None | null | | True | true | | False | false | | int | int | | long, float | Number | | str, unicode | String | | dict | Object | | list, tuple | Array | | xml.dom.minidom.Document | XML, XMLDocument | | datetime | Date |

AS3 -> Python

| AS3 | Python | |:----|:-------| | null | None | | undefined | None | | true | True | | false | False | | int | int | | Number | float | | String | unicode | | Object, MixedArray | dict | | Array | list | | XML, XMLDocument | xml.dom.minidom.Document | | Date | datetime |

Encoding

  • Use the amfast.encoder.Encoder class to encode objects.

Encoder

  • amf3 - bool - True to encode as AMF3.
  • use_collections - bool - True to encode lists and tuples as ArrayCollections.
  • use_proxies - bool - True to encode dicts as ObjectProxies.
  • use_references - bool - True to encode multiply occurring objects by reference.
  • use_legacy_xml - bool - True to encode XML as XMLDocument instead of e4x.
  • include_private - bool - True to encode attributes starting with an underscore.
  • class_def_mapper - amfast.class_def.ClassDefMapper - The object that retrieves ClassDef objects.
  • buffer - file-like-object - Output buffer. Set to None to output to a string.

``` from amfast.encoder import Encoder

Encode an object to AMF0

encoder = Encoder(amf3=False) encoded = encoder.encode(obj)

Encode an object to AMF3

encoder = Encoder(amf3=True) encoded = encoder.encode(obj)

Encode an AMF Packet

encoded = encoder.encode_packet(packet_obj)

If the 'buffer' attribute

of the encoder is not set,

the return value of 'encode'

method is a string.

#

If the 'buffer' attribute

is set, the return value is

the buffer object.

```

Decoding

  • Use the amfast.decoder.Decoder class to decode objects.

Decoder

  • amf3 - bool - True to decode as AMF3.
  • class_def_mapper - amfast.class_def.ClassDefMapper - The object that retrieves ClassDef objects.

``` from amfast.decoder import Decoder

Decode an object from AMF0

decoder = Decoder(amf3=False) obj = decoder.decode(encoded)

Decode an object from AMF3

decoder = Decoder(amf3=True) obj = decoder.decode(encoded)

Decode an AMF Packet

packet_obj = decoder.decode_packet(encoded) ```

Custom Type Maps

  • AmFast supports user-defined object types.
  • Use a amfast.class_def.ClassDef object to define how custom objects are serialized/deserialized.
  • Use a ClassDefMapper to map amfast.class_def.ClassDef to an object alias.

``` from amfast import class_def

ClassDefMapper objects keep track of ClassDefs

class_mapper = class_def.ClassDefMapper()

Map a custom class with static attributes

class_mapper.mapClass(class_def.ClassDef(MyCustomClass, 'class.alias', ('tuple', 'of', 'static', 'attribute', 'names')))

Object attributes can be automatically converted

to/from a specific type with the

encode_types and decode_types attributes.

#

encode_types and decode_types are dictionaries where

the keys are the names of the attributes to convert,

and the values are functions that will perform the conversion.

mapped_class = class_def.ClassDef(MyCustomClass, 'class.alias'.... mapped_class.encode_types = {'attribute_to_convert_to_int_before_encoding': int} mapped_class.decode_types = {'attribute_to_convert_to_int_after_decoding': int}

Map a custom class with dynamic attributes

class_mapper.mapClass(class_def.DynamicClassDef(MyCustomClass, 'class.alias', ()))

Map a custom class implementing IExternalizable

ExternClassDef must be sub-classed, and the

methods readExternal and writeExternal must be implemented.

class_mapper.mapClass(class_def.ExternClassDef(MyCustomClass,'class.alias'))

Map a custom class that is also mapped with SQLAlchemy.

Attributes mapped with SQLAlchemy will automatically be

added to the list of static attributes.

class_mapper.mapClass(class_def.sa_class_def.SaClassDef(MyCustomClass, 'class.alias')

Attach ClassDefMapper to Encoder and Decoder

objects to use the ClassDefMapper for encoding

and decoding

encoder.class_def_mapper = class_mapper decoder.class_def_mapper = class_mapper

Use custom class mappings with a Channel

channel = channel_set.getChannel('channel_name') channel.endpoint.encoder.class_def_mapper = class_mapper channel.endpoint.decoder.class_def_mapper = class_mapper ```